1. Field
One or more embodiments relate to a lithium titanate, a negative electrode for a lithium secondary battery that includes the lithium titanate, and a lithium secondary battery including the negative electrode.
2. Description of the Related Technology
Lithium titanate (Li4Ti5O12) is useful as an electrode material in a lithium secondary battery.
Usually, lithium titanate is prepared by dry-heat treating a mixture including titanium dioxide and a lithium compound, or by using other dry or wet powder synthesis methods that are known to one of ordinary skill in the art.
Conventionally, lithium titanate is obtained from titanium dioxide as a starting material. In preparing an electrode material having excellent characteristics, titanium dioxide, as a starting material of lithium titanate, plays an important role. Among a lithium precursor and a titanium precursor, which are necessary starting materials of lithium titanate, an amount of the titanium precursor needed in consideration of a composition ratio with respect to the lithium precursor is relatively high and thus, the kind and amount of elements contained in the titanium precursor affects battery performance more than those in the lithium precursor. Also, in consideration of a percentage of the titanium precursor in the total raw material costs, it is important to select an appropriate titanium precursor. When high-purity titanium dioxide is used as a precursor of lithium titanate, many problems including high manufacturing costs may occur.
Lithium titanate undergoes a small volumetric change during charging and discharging and thus has excellent rapid charge and discharge characteristics, and when used in a lithium battery, the lithium battery has high-performance characteristics. Accordingly, it is expected that lithium titanate is very useful as an electrode material of a high-output battery used in an application, such as a hybrid electric vehicle, that requires rapid charging and discharging.
An important characteristic of a high-capacity middle and large-sized battery is rate capacity. However, lithium titanate has lower charge and discharge capacity than a conventional graphite-based negative active material. Thus, there is a need to embody a capacity near a theoretical value and improve capacity retention characteristics by control of impurities in the active material.